Scope shimming, sav...
 
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Scope shimming, save those tubes


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(@jiminpgh)
Joined: 3 years ago
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Perfect size and diameter for droop compensation

shim

.


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(@marflow)
Joined: 3 years ago
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ah when the epoxy is gone use the packaging up also, good tip 

and i think if you have a non recoiling application use 30mm rings with inserts for your 1 inch scopes, save the tube 


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airmojo
(@airmojo)
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I used 35mm film before... many years ago before digital cameras got so popular... do them still make the stuff (35mm film) ?

I admit I always wondered what else could be used...

And remember reading on one of airgun forums that you shouldn't shim you scopes, instead use a drooper mount or an adjustable mount, but the adjustable mounts always seemed over complicated and fidgety to get set right... have several drooper mounts and not one adjustable mount.


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(@scottblair)
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I've used aluminum soda can material. Just cut strips with scissors. Will conform easily to the scope cradles radius.


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(@jiminpgh)
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Posted by: @scottblair

I've used aluminum soda can material. Just cut strips with scissors. Will conform easily to the scope cradles radius.

Beer can aluminum works better than soda can aluminum, for several reasons.

 


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Gratewhitehuntr
(@gratewhitehuntr)
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Posted by: @jiminpgh
Posted by: @scottblair

I've used aluminum soda can material. Just cut strips with scissors. Will conform easily to the scope cradles radius.

Beer can aluminum works better than soda can aluminum, for several reasons.

 

Beer has higher lubricity than soda.

 


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(@austin870)
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Shimming is not good for scopes.  It is torqueing the scope barrel by being off center.  People lap rings so the rings themselves have no off center torque.  Now if it is an $89 Bugbuster etc who gives a crap.   I would not do it with a $300+ scope. Many people overtorque their rings and don't realize using blue loctite adds 5 to 7 pounds of torque after it dries. Sometimes you get damage from things and sometimes not. There are a lot of factors and what worked for one situation may not work for another.  

The Burris Signature rings allow you to shim without damage.  The fixed droop mounts work really well.  I agree the adjustable ones are a pain but they do work. 


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Limbshaker
(@limbshaker)
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I just bend the barrel and be done with it. 

Underlevers, break barrels, whatever. 

Takes less time than adjusting an adjustable mount and costs nothing. 


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(@austin870)
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Every gun I have seen where someone bent the barrel I could see it.  From then on it would bug me although just cosmetic.  I watched a guy do an experiment to prove a bent barrel has no affect on group size or accuracy.  He took an airgun barrel and bent it into a complete loop with the barrel coming out the front of the gun.  The group size was identical and he shot a lot.  Pellet like and dislike were the same.  I could not believe it.  


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Limbshaker
(@limbshaker)
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Posted by: @austin870

Every gun I have seen where someone bent the barrel I could see it.  From then on it would bug me although just cosmetic.  I watched a guy do an experiment to prove a bent barrel has no affect on group size or accuracy.  He took an airgun barrel and bent it into a complete loop with the barrel coming out the front of the gun.  The group size was identical and he shot a lot.  Pellet like and dislike were the same.  I could not believe it.  

Most of the ones that need it, you can see the "droop" before they are corrected. Afterwards they are pointing the direction they need to be, and look right. But these are just the ones I've done. 

It's crazy how easy an HW77K barrel will bend, and how insanely stiff a FWB300 is. 


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(@austin870)
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Posted by: @limbshaker
Posted by: @austin870

Every gun I have seen where someone bent the barrel I could see it.  From then on it would bug me although just cosmetic.  I watched a guy do an experiment to prove a bent barrel has no affect on group size or accuracy.  He took an airgun barrel and bent it into a complete loop with the barrel coming out the front of the gun.  The group size was identical and he shot a lot.  Pellet like and dislike were the same.  I could not believe it.  

Most of the ones that need it, you can see the "droop" before they are corrected. Afterwards they are pointing the direction they need to be, and look right. But these are just the ones I've done. 

It's crazy how easy an HW77K barrel will bend, and how insanely stiff a FWB300 is. 

I thought the droop problem came from being setup from the factory for open sights. Then most people have their scope way high off the barrel on springers insead of 1/8" with rimfires.  I agree the FWB300 is a tank and so boringly accurate.  You have to try and miss hitting things. I found it more controlable than most PC's. If they made a clone of those at that quality level now they would be well over $2000. 


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nervoustrigger
(@nervoustrigger)
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Posted by: @austin870

Many people overtorque their rings and don't realize using blue loctite adds 5 to 7 pounds of torque after it dries.

Please note, threadlocker does not cause the torque to increase as it cures.  Not the torque on the fasteners and not the torque acting on the scope tube.  Perhaps you are accidentally conflating this concept with breakaway torque—the torque necessary to remove the fastener.  


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crazyhorse
(@crazyhorse)
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I prefer business cards myself. 


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Frank in Fairfield
(@frank-in-fairfield)
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Bleach bottle


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Gratewhitehuntr
(@gratewhitehuntr)
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Posted by: @nervoustrigger
Posted by: @austin870

Many people overtorque their rings and don't realize using blue loctite adds 5 to 7 pounds of torque after it dries.

Please note, threadlocker does not cause the torque to increase as it cures.  Not the torque on the fasteners and not the torque acting on the scope tube.  Perhaps you are accidentally conflating this concept with breakaway torque—the torque necessary to remove the fastener.  

This, breakaway torque, and it couldn't be a flat number like 5-7, due to the drastic variations in surface area between fasteners.

That's the simple explanation, without taking fastener stretch into account, or trying to figure out how locktite would change something in stretched fasteners.

 

Put a trashy allen wrench in the fastener, heat the wrench red hot with your cracklighter, wait for the heat to soak into the fastener, use a non-annealed wrench for fastener removal. Locktite now adds minimal breakaway torque.

 

Welcome to the forum Austin.

The droop problem, comes from a bore which is not aligned with the mounting system on the receiver.

There are also swoop problems, for a barrel which points up.


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(@austin870)
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Posted by: @nervoustrigger
Posted by: @austin870

Many people overtorque their rings and don't realize using blue loctite adds 5 to 7 pounds of torque after it dries.

Please note, threadlocker does not cause the torque to increase as it cures.  Not the torque on the fasteners and not the torque acting on the scope tube.  Perhaps you are accidentally conflating this concept with breakaway torque—the torque necessary to remove the fastener.  

Actually that is the standard answer from Vortex techs.  The most common question they are asked is why is my POI wandering.  Their answer is the rings are too tight.  Their techs have also tested the loctite to be increasing the pressure specifically 5 to 7 pounds.  They give that answer because it solves more POI shift problems than every other answer put togeather.  There is a video on Youtube where Votex goes over this POI shift and their loctite testing.  I will admit breakaway torque makes more sense and would be WAY easier to measure.  Perhaps Vortex just derives their assumption based on the bereakaway torque. Not very professional but I have seen worse "testing".  


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nced
 nced
(@nced)
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@austin870

"There are a lot of factors and what worked for one situation may not work for another."

I've had scope tube damage using a normal 15in/lbs of top strap screw torque using two piece BKL "double strappers", however the scope slipped in the same rings using 10in/lbs torque.........

 

 

I never had scope tube damage using the BKL one piece mount using 15in/lbs top strap screw torque, however the scope would slip in the rings unless lined with electrical cloth friction tape, however I never did solve the scope base slipping on the receiver dovetail even though I use 40in/lbs base screw torque which is 5in/lbs above the BKL max recommended torque.......

 

I stopped using both the BKL 2 piece and one piece mounts after trying the UTG Universal Dovetail to Picatinny adapter and Weaver/Picatinny rings.......

 

 

With my 1" tube scopes I found that the cheap Weaver Quad Lock rings would hold my scope solidly with only 10in/lbs torque, however the scope tubes aren't damaged using 15in/lbs torque. I believe that the "wrap around style" of the top straps is the reason for this...........

 

The Weaver Quad Locks aren't available for 30mm scope tubes so I found this set of rings that works well with my rather short Hawke AirMax Compact scope allowing clearance between the scope "bells". they also hold my scope solidly and don't damage my scope tube with 15in/lbs torque. I never tried this set of rings "bare" but I lined the rings with friction tape like I did when I used the one piece BKL mount.....

 

 

Anywhoo, to not be bothered with adjustable mounts the first thing with a new scope is check how the reticle reflection aligns with the reticle in the mirror. Normally the new scope are optically centered before leaving the factory so if the alignment in the lighted mirror is good I use the "mirror method" for all optical centering. The next thing I do is to mount the scope and shoot some groups to check the zero and then bend the barrel as needed to get the poi within about 1" of the poa at 30 yards and the fine adjustments are done with the scope turrets. Then the turret caps are loosened and adjusted till the "0" aligns with the marker and the turret cap is snugged up for use..........

Target used to judge the barrel alignment at 18 yards before going to the shooting lane and target at 30 yards.........

 

My barrel tweaking gizmo (and even a "barrel tweaking tree" if needed.........

 

 

 

As a side note, barrels are often bent after installing.........

 


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(@jiminpgh)
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nced
 nced
(@nced)
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@jiminpgh

Interesting stuff that I think I'll try. Does this stuff affect the bluing on a receiver?


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(@austin870)
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@nced  Exceptional post and one pile of great info.  Great jigs for bending barrels as well as good lighting on the pics. I can remember seeing every problem with creep and compression you posted when shooting magnum or just springers above 12ftlbs.  I don't shoot either anymore. I use PCP for anything over 12ftbls and I just find that a more comfortable and perhaps more accurate "for me" shooting power with a springer.  I have phased out all my springers but my last couple which are all customized with fancy stocks etc.

I understand using light torque the scope can slip. What I do to maintiain lower torque values is I use rubber cement inside the rings.  Actually contact cement works even better for higher fps springers.  Both are great for also stopping any ring marks and the scopes pop out with little effort when needed.  I found they work better than friction tape and take up less room in the rings.   

The base moving is a whole other matter and another reason I don't own any springers more than 12ftlbs anymore. I did the magnum springer dance for awhile and learned a lot about springers and scopes but it was not for me.  I am also a huge fan of the dovetail to picitinny adapters and they are cheap. I found the Burris Signature rings to work very well but they are such a pain to dial in on springers with droop.  

You have a nice tree there.  When I was looking for one to do barrels just the right notch suddenly became impossible to find.  


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nced
 nced
(@nced)
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@austin870

"when shooting magnum or just springers above 12ftlbs."

When I first started shooting hunter class field target matches decades ago my scope with duplex reticles (4-16 x 40 Bushnell Elite 4200) was used for "scope rangefinding" and I found that If I shot 7.9 grain boxed Crosman Premiers at about 910fps (about 14 1/2fpe) the trajectory fit the reticle nicely like this.......

In later years I started using "dotted reticles" and with the larger number of hard aiming points the pellet trajectory matched the reticle similar this pic so I've been tuning my .177 HW95 and .177  Beeman R9 to shoot CPLs at about 850fps (about 12 1/2 fpe)........

 

 

"I use rubber cement inside the rings."

Hummm....rubber or contact cement inside scope rings, might have to give that a try because the friction tape does work well to stop the "slippies", however isn't exactly thin..........

 

"I found the Burris Signature rings to work very well but they are such a pain to dial in on springers"

I initially tried a couple brands of adjustable mounts and also found that mounting the scope, shooting a group, unmounting the scope to adjust "finneky screws", remount the scope and shoot another group until the poi was where it was supposed to be was too much of a hassle, especially if I didn't torque the "finneky screws" properly and the mount loosened up and shifting during the season of WV squirrel hunting!

 

"I was looking for one to do barrels just the right notch suddenly became impossible to find."

The "tweakin' tree" is useful for adding either windage or snoop to a barrel however it's pretty useless for adding droop to a break barrel. That's why I made up a "barrel bender" from construction lumber, an eye bolt, nut and washer. The bending of a barrel with the jig is much more controlled and easy to reverse if the bend is a bit excessive.


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(@jiminpgh)
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Posted by: @nced

@jiminpgh

Interesting stuff that I think I'll try. Does this stuff affect the bluing on a receiver?

Yes it does, a little bit. It is, after all, an abrasive in a volatile medium. That's why I say to use it very judiciously. A tiny drop on the tip of a toothpick on each clamping shoe is all it takes.  That won't leave a mark, and will remain there for future re-mounts. Too much will definitely F things up. It is crystalline Aluminum Oxide at a very fine-grain structure, and it will permanently embed into the scope grooves and the mount clamps.

I've found that, once treated with this stuff, I can swap scopes and mounts between guns without a hint of creep. No need to ever re-apply.

But again, I Strongly caution to use the smallest amount you can get on the tip of a toothpick.

Read the SDS on this stuff before you use it. A VERY little goes a long way. But it DOES work to keep mounts from moving in the grooves.

BTW, it's ALSO great for its intended use, which is to keep drivers from camming out of fasteners. Saved my a$$ on many an automotive project!

 


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nced
 nced
(@nced)
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@jiminpgh

The reason I questioned is because a while back I used fine automotive valve grinding compound on my R9 dovetails to keep a one piece BKL mount from shifting and it did remove the bluing. Perhaps the reason was that I used too much or even the fine abrasive was too coarse.

Anywhoo, I ordered a container to try.

https://ezgrip.net/

From the above link..........

"The Commercial Grade solution has thousands of hardened aluminum cubes"

Yep....does seem like aluminum oxide abrasive to me. 😀 


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nced
 nced
(@nced)
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EZ grip arrived today so I'll be testing it with my UTG Dovetail To Picatinny Adapter without using a stop pin. I'll be torquing the horizontal base screws to the max recommended 25in/lbs torque and see if there is any scope mount slippage after a couple hundred shots from my .177 cal HW95 tuned to shoot 7.9 grain CPLs @ 850fps (about 12.5fpe)


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nced
 nced
(@nced)
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Posted by: @nced

EZ grip arrived today so I'll be testing it with my UTG Dovetail To Picatinny Adapter without using a stop pin. I'll be torquing the horizontal base screws to the max recommended 25in/lbs torque and see if there is any scope mount slippage after a couple hundred shots from my .177 cal HW95 tuned to shoot 7.9 grain CPLs @ 850fps (about 12.5fpe)

Well....I tested out the E-Z grip in my HW95 dovetails tuned to 12.5fpe without a stop pin and it did help SOME, however not enough to stop using a stop.

The UTG adapter clamp screws were was initially torqued to my mount recommended 25in/lbs torque and the rear edge of the base was aligned with the center of the safety button. Slippage  shown was after only 20 shots............

Today I remounted the adapter with scope using E-Z Grip and it did help reduce "slippage" but still not satisfactory. Again thew rear edge of the adapter was aligned with the center of the safety button and I had this amount after 45 shots..........

 


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